Description
- Abstract:
- Recent astrophsyical observations indicate that about 23% of the matter in the universe exists as non-luminous, non-baryonic dark matter. General thermodynamic arguments suggest that if an as-yet undiscovered weakly interacting particle were in thermal equilibrium in the early universe, it could have a cosmologically interesting relic abundance today. Dark matter particles are predicted to have collapsed into isothermal halos on a galactic scale. Minimal super-symmetric extensions of the standard model predict the existence of a stable particle with a mass in the range 10-1000 GeV c<sup>-2</sup>, and a an interaction cross section with ordinary matter σχ < 10<sup>-36</sup> cm<sup>2</sup>. For the past two decades, numerous experiments have been deployed with the aim of direct or indirect detection of dark matter. XENON10 is a direct-detection liquid Xe experiment, with event-by-event 3D position reconstruction. Since dark matter does not interact electromagnetically, it's signature in a Xe detector is expected to be a low-energy nuclear recoil. Particle interactions in Xe create scintillation light (<em>S</em>1) and ionization. The ionization is drifted across the active Xe target and converted into a proportional scintillation signal (<em>S</em>2) by an external electric field. The ratio y = log10(<em>S</em>2/<em>S</em>1) is larger for β and ɣ background events than for nuclear recoils, as determined by neutron calibration data. This allows event-by-event discrimination of background from the expected signal. In 2007 XENON10 eclipsed CDMS II as the most sensitive direct-detection experiment, excluding the existence of particle dark matter with a cross-section (normalized to a single nucleon) σχ > 10<sup>-43</sup> cm<sup>2</sup> at a particle mass of 100 GeV c<sup>-2</sup> (90% C.L.). Liquid Xe technology is extremely promising since it is easily scaled to larger target mass, which will allow greater sensitivity to particle dark matter interactions. I discuss the XENON10 detector, deployment, operation, analysis and dark matter exclusion results. I also present a new method to determine the light yield of Xe for nuclear recoils, which is essential for calibrating the nuclear recoil energy scale and understanding the detector threshold.
- Notes:
- Thesis (Ph.D. -- Brown University (2008)
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Citation
Sorensen, Peter F.,
"A Position-Sensitive Liquid Xenon Time-Projection Chamber for Direct Detection of Dark Matter: The XENON10 Experiment"
(2008).
Physics Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0V1231M
